The successful reproduction of farm animals is fundamental for the productivity of livestock because it directly determines the birth of the young intended for meat production and, indirectly, the beginning of a lactation period which is prolonged by milking milk-producing animals.
Among these animals, the females accept being mounted only when they are in heat (oestrus), i.e., during a very short period (between 36 and 48 hours) of their reproductive cycle which lasts from 17 days (ovines) to 21 days (bovines and goats). The expression of this oestrus is more or less clear, depending on the species: undetectable in the absence of males among ovines and goats and noticeable among bovines because of the fact that the cow in heat allows herself to be mounted by others and shows signs of excitement. Reproduction is also a key step in genetic improvement of animals since females can be artificially inseminated with sperm from animals considered to be improving the breed. However, these inseminations must be carried out at a precise moment in relation to the appearance of heat among these females.
For the detection of the heat condition, in most cases, the stock-breeders rely on the observation of the cows but the rate of detection is low, because cows exhibit their heat condition more during the night time hours than during the day. As far as small ruminants are concerned, at present the only solution to perform artificial insemination relies on inducing heat in the females by hormonal treatments and programmed insemination. The use of hormonal treatments is limited with bovines. These days, on account of the principle of precaution demanded by consumers, one must seriously consider that the use of hormonal treatments in order to induce the fertility cycle among livestock, may become heavily regulated. If this possibility were to become reality, it would be virtually impossible to carry out inseminations on a large scale among small ruminants. In effect, considering the size of the herds (frequently 300 to 600 head), it is not feasible to detect oestrus by observing, several times each day, the behavior of the males in the herd. The same problem arises for bovines for which the number of heads per herd are increasing noticeably. There is thus a need to automate the detection of females in heat in large herds, either to achieve a greater number of natural couplings with a record of paternity, or for artificial insemination.
At present there are devices for detecting the females in heat which rely on measuring the agitation of cows (pedometers distributed by AlfaLaval [in France]) and on the analysis of variations in milk production and/or of milk characteristics (pH). Other systems, which are much more cumbersome consist of video monitoring of an area set aside for animals susceptible to come into heat.
These systems are costly, and their setup is complicated. Actually they require regular visual surveillance by an observer or a biochemical analysis, and they are liable to falsely identify females in heat.
There are other electronic devices for detecting females in heat which are exclusively used for bovines. These are pressure detectors that are temporarily attached on the cow's rump. Being mounted by another cow (which is not so equipped and which can be any cow) triggers a signal which is recorded in the device. In the case of the DEC ([electronic heat detection] system which features a visual alarm and which is sold by IMV France) the frequency at which the LED worn by the cow flashes, indicates the intensity and the frequency of the mountings and allows the stock-breeder to decide whether insemination should be done. Another system exists (known under the name of HEATWATCH (™), registered trade name, USA) which relies on the same principle, but each time the cow is mounted, her device sends data to a wireless access point which relays this signal to a computer. The cow can be identified by her number which is manually entered when the device is installed. Another more recent system uses 78 radio channels to identify the cows that are being mounted (this does not represent the official number of the animal, but a temporarily assigned number, in difference to the HeatWatch system).
All these systems are costly and their installation is complex. All females must be successively and temporarily equipped so their period in heat can be detected.
In general, all existing detectors make use of female-female behavior which are much less selective than the male-female behavior. As a matter of fact, the cows in heat accept being mounted, but they also try to mount the other cows (not in heat). This weak selectivity of cow-cow relations leads to a high number of false positives.
The present invention aims to remedy these inconveniences.